Time delay bimetallic relay

ABSTRACT

A relay employing two slotted bimetallic blades mounted substantially parallel and overlapping at their free (unmounted) ends with a heater element associated with one of the blades.

' [72] Inventor [45] Patented 3,108,166 10/1963 Bakeretal United StatesPatent Mulio 0. Sq): Newark, NJ.

835,564 June 23, 1969 Aug. 24, 1971 Wagner Electric Corporation 21 Appl.No. 22 Filed [73] Assignee [54] TIME DELAY BIMETALLIC RELAY 3 Claims, 2Drawing Figs.

[52] U.S.Cl 337/101,

' 3.37/102, 337/111 [51] Int. Cl 11011137110, 1-l01h 37/52, HOlh 61/04[50] FieldolSelrch 73/3635;

[56] I References Cited UNITED STATES PATENTS 3/ 1969 Vind PrimaryExaminer-Bemard A. Gilheany Assistant Examiner-Dewitt M. MorganAttorney-Eyre, Mann & Lucas ABSTRACT: A relay employing two slottedbimetallic blades mounted substantially parallel and overlapping attheir free (unmounted) ends with a heater element associated with one ofthe blades.

PATENTEBAus24|97| 3601.736

INVENT R MA/VL/O 6 B 23 5 ATTOR EYS TIME DELAY BIMETALLIC RELAY Thepresent invention relates to a relay employing two slotted, overlappingbimetallic blades, preferably with a contact mounted on the overlappingend of each blade, the other ends of the blades being rigidly mounted toterminals extending through an insulating base. The slotted blades areblades, and therefore deflect more rapidly. The free ends of to coolmore rapidly then the ordinary solid, rectangular blades, and thereforedeflect move rapidly. The free ends of for the blades deflect in thesame direction when the ambient temperature changes, thus compensatingfor any variations in ambient temperature. Also, since the blades are ofsubstantially the same shape, load current passing through the bladeswhen their free ends are in contact causes substantially the sameincrease in temperature of each blade, thereby causing substantially thesame deflection of each blade.

A further advantage of employing bimetallic blades which are slottedalong major portions of their length is that the blades may be madewider and thicker, i.e., the bladesmay be larger in the verticaldimensions of FIG. 1 and FIG. 2, respectively.- Previously, the bladeswere made either very thin or with greatly reduced width in order tokeep the blade mass within acceptable limits. The reduction in widthmade machine-handling of the blades much more difficult. Reducing thethickness of the blade resulted in frequent cutting of the insulatedheater wire, which is machine-wrapped around the active blade in theprocess of mass manufacture, because of the resulting thin blade edges.These serious disadvantages are overcome by the slotted bimetallicblades employed in the bimetallic relay embodying the present invention.Also, slotting enables the formation of longer bimetallic blades, i.e.,blades greater in the horizontal dimension of FIGS. 1 and 2. This inturn facilitates the adjustment of the gap between the contacts, whichadjustment is carried out by twisting either or both of the terminals onwhich the blades are mounted.

A better understanding of the present invention may be had by referenceto the accompanying drawings, of which:

FIG. I is a side elevation of an embodiment of the present invention; 7

FIG. 2 is a top elevation of an embodiment of the present invention.

Referring now specifically to FIG. 1, the slotted bimetallic blades 2and 4 are mechanically and electrically connected to terminals 6 and 8,respectively, which terminals extend through a base 10 formed of aninsulating material, which is preferably substantially rectangular inshape. The heater element 12, which may consist of a resistive wirecoated with an insulating material, is wrapped around active blade 2. Inthe embodiment shown, terminals 14 and 16 extending through the base 10serve to connect heater element 12 to a source of current. However, insome applications it may be desirable to have heater element 12connected' between the blade-supporting terminals 6 and 8, therebyobviating the need for terminals 14 and 16.

Referring now specifically to FIG. 2, the free end of active blade 2 andthe free end of compensating blade 4 may be seen to overlap near thecenter area of the base 10. In the preferred embodiment of the presentinvention, contacts 18 and are mounted in the respective areas ofoverlap of blades 2 and 4. These contacts are not required to form anoperative device however. As is shown in this figure, the blades 2 and 4are substantially parallel to one another.

The operation of the relay illustrated in the drawings is as follows:

When terminals 6 and 8 are connected in a load current path which is tobe controlled, and terminals 14 and 16 are connected to a controllingsource of current, the passage of heating current through heater element12 will cause active blade 2 to deflect toward compensating blade 4.Thus, blademounted contacts 18 and 20, which are normally open in theembodiment shown, will be brought into engagement. With contacts 18 and20 closed, the controlled load current path will be closed throughterminal 6, blade 2, contacts 18 and 20, blade 4, and terminal 8. Theheating effect of load current passing through blades 2 and 4 isneutralized by offsetting increments of deflection of both blades 2 and4. Whatever increment of deflection of active blade 2 results fromload-current heating, compensating blade 4 will move an equal increment,since both blades 2 and 4 are of the same materials and havesubstantially the same geometry, and therefore have substantially thesame resistance. When the controlling heating current is reducedsufficiently, the active blade 2 will cool and cause contacts 18 and 20to disengage. Thus, load current ceases to flow through both blades 2and 4, which will then return to their normal or equilibrium positions.In the equilibrium position, the positions of the contacts 18 and 20relative to one another will remain constantover a wide range of ambienttemperatures, since any increment of deflection by one blade as a resultof change in ambient temperature will be offset by a correspondingincrement of deflection by the other blade.

The slots extending along the length of the bimetallic blades 2 and 4enable faster reaction by the blades to changes in temperature, i.e.,both heating and cooling, for the reason that the value of the ratio ofblade surface area to blade mass is greatly increased over the value ofthat ratio for solid rectangular blades. Thus, the rate of heat transferfor the slotted blades is greater than for the solid blades.

Although the relay illustrated in the drawings and described above hasnormally open contacts, by proper choice and orientation of thebimetallic blades relative to one another, a device embodying thepresent invention may be constructed with normally closed contacts. Insome applications, it might be desirable to have a second heater elementassociated with the compensating blades. This second heater elementcould be controlled from the same current source as the first heaterelementor from a separate source.

The advantages of the present invention, as well as certain changes andmodifications to the disclosed embodiment thereof, will be readilyapparent to those skilled in the art. It is the applicants intention tocover all those changes and modifications which could be made to theembodiment of the invention herein chosen for the purposes of thedisclosure without departing from the spirit and scope of the invention.

I claim:

1. A bimetallic relay comprising:

a. a base formed of insulating material;

b. a plurality of terminals extending through said base;

c. first and second substantially parallel bimetallic blades slottedalong major portions of their respective lengths and connectedmechanically and electrically to first and second terminals,respectively, said blades having sub stantially the same electricalresistance and extending toward each other between said terminals andoverlapping at their free ends;

d. first and second contacts mounted on the overlapping portions of saidfirst and second bimetallic blades, respectively; and

e. a heater element wound around said first bimetallic blade andelectrically connected between two of said plurality of terminals,whereby said free ends of said first and second bimetallic blades willmove through equal offsetting increments of deflection when subjected tochanges in ambient temperature over a wide range of ambienttemperatures, and load-current heating of said first and secondbimetallic blades will also cause said free ends of said blades to movethrough equal offsetting increments of deflection when said contacts areclosed.

2. A bimetallic relay according to claim 1 wherein said heater elementis connected between third and fourth terminals.

3. A bimetallic relay according to claim 1 wherein said heater elementconsists of a resistive wire coated with an insulating material.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 ,601.,T56 DatedAugust 2 4 19 Z l inventor(s) Manlio 0. Sept? It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Patent No.

Col. 1, Lines 1? to 10 should read:

--ing through an insulating base. The slotted blades are able to coolmore rapidly than the ordinary solid, rectangular blades and thereforedeflect more rapidly, The free ends of the blades-- Signed and sealedthis 1mm day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSC HALK Attestinp, Officer Comissionerof Patents DRM FWD-1050 (1 7 USCOMM-DC eons-P69 Q LLS GOVERNMENT PRINHNGOFFICE {959 0*356334

1. A bimetallic relay comprising: a. a base formed of insulatingmaterial; b. a plurality of terminals extending through said base; c.first and second substantially parallel bimetallic blades slotted alongmajor portions of their respective lengths and connected mechanicallyand electrically to first and second terminals, respectively, saidblades having substantially the same electrical resistance and extendingtoward each other between said terminals and overlapping at their freeends; d. first and second contacts mounted on the overlapping portionsof said first and second bimetallic blades, respectively; and e. aheater element wound around said first bimetallic blade and electricallyconnected between two of said plurality of terminals, whereby said freeends of said first and second bimetallic blades will move through equaloffsetting increments of deflection when subjected to changes in ambienttemperature over a wide range of ambient temperatures, and load-currentheating of said first and second bimetallic blades will also cause saidfree ends of said blades to move through equal offsetting increments ofdeflection when said contacts are closed.
 2. A bimetallic relayaccording to claim 1 wherein said heater element is connected betweenthird and fourth terminals.
 3. A bimetallic relay according to claim 1wherein said heater element consists of a resistive wire coated with aninsulating material.